Applying of adhesives

ABSTRACT

This invention concerns a paster for applying especially a lowviscosity hot-melt to a vertical workpiece. The adhesive is pumped to the upper end of a vertical groove from which a pickup drum receives adhesive which is transferred to the workpiece by a vertical transfer drum which has sponge rubber transfer members which roll in contact with pitted areas on the pickup drum to receive adhesive.

11110 all States Patent inclhlcliliie et a1.

[45 1 Mai, M, W)

AlPlPLi/HNG 01F ADHESIVES Dennis Hinchclifie; Henry James Hubbard, both of Deptford, England Molins Machine Company Limited, London, England Filed: Sept. 2, 1969 Appl. No.: 854,521

Inventors:

Assignee:

Foreign Application Priority Data July 10, 1969 Great Britain ..34,786/69 Int. Cl. ..BOSc 11/00 lField of Search ..1 18/265, 266, 202, 212, 203, 118/239, 204, 258, 238

[56] Metereim Cited UNITED STATES PATENTS 2,641,219 6/1953 Tranter ..118/212 3,391,673 7/1968 Knapp eta1. ..118/212 1,957,470 5/1934 Milmoe 1 18/204 X 2,170,218 8/1939 Rosenberg. ...118/258 X 3,030,915 4/1962 Shannon ..1 18/202 Primary Examiner-Mervin Stein Assistant Examiner-Leo Millstein Attorney-Craig, Antonelli & Hill [5 7] ABSTMAQT This invention concerns a paster for applying especially a lowviscosity hot-melt to a vertical workpiece. The adhesive is pumped to the upper end of a vertical groove from which a pickup drum receives adhesive which is transferred to the workpiece by a vertical transfer drum which has sponge rubber transfer members which will in contact with pitted areas on the pickup drum to receive adhesive.

12 Claims, 5 Drawing ll igures Pmmmmd March 14,1972 3,648,651

3 Sheets-Sheet 2 Pammd March 14, R972 3 Sheets-Sheet 5 APPLYING OF ADHESIVIES This invention is particularly concerned with applying lowviscosity adhesives, for example with a viscosity of say between 250 and 750 centipoises, and especially hot-melt adhesives, that is to say adhesive which is applied hot in a liquid state and which then sets on cooling. Apparatus according to this invention may however in general be used to apply to the face of a workpiece a film of any liquid material, especially where the film is to be applied to closely defined areas of the workpiece face. For convenience the liquid will be referred to as an adhesive, but it should be understood that apparatus according to this invention can be used for applying other liquids.

This invention has two features which may be used separately but are preferably used in combination, especially in the case of apparatus for applying a low-viscosity hot-melt adhesive.

The first feature of this invention is particularly concerned with the problem of applying an adhesive to a vertical surface. This applies particularly in the case of a packing machine which rotates about a vertical axis and carries past the adhesive apparatus sheets which are to be formed into packets and which are held vertically by the machine while adhesive is being applied; an example of such a packing machine is described in our French Pat. No. 1,498,097.

According to the first feature of this invention, apparatus for applying especially a low-viscosity hot-melt adhesive to a vertical workpiece, for example a sheet or web of paper, comprises a pickup drum mounted in a housing for rotation about a vertical axis, an adhesive input for delivering adhesive from a reservoir to the upper end ofa vertical groove in the housing from which the drum picks up adhesive while rotating, and an adhesive return passage for returning excess adhesive from the bottom end ofthe groove back to the reservoir.

During use the workpiece may move, preferably with a rolling action, directly in contact with the pickup drum. Preferably, however, it moves in contact with a transfer drum which receives adhesive from the pickup drum, by rolling in contact with it, and transfers the adhesive to the workpiece; this is preferably achieved in accordance with the second feature of this invention.

According to the second feature of this invention, apparatus for applying in particular a low-viscosity hot-melt adhesive to at least one predetermined area of a workpiece (for example paper to be formed into a packet) includes a pickup drum which rotates adjacent to a pool of adhesive so as to pick up adhesive on its surface, and a transfer drum which is arranged to roll in contact with the pickup drum and with the workpiece and has at least one transfer surface which stands proud from the main cylindrical surface ofthe drum and is shaped so as to apply the desired adhesive pattern to the predetermined area of the workpiece, the transfer surface being on rubber or a rubberlike material, (preferably in a sponge form), secured to the main body of the drum. The areas of the pickup drum from which the transfer drum receives adhesive are preferably pitted.

The sponge rubber preferably has a high proportion of interconnecting cells. It may be formed by mixing the rubber material with soluble crystals (for example salt) which are subsequently dissolved out, for example by boiling in water. A suitable silicone rubber sponge may for example be made by mixing the basic material with about 1% times its weight of sodium chloride crystals.

An example of apparatus according to this invention which will be termed a paster is shown in the accompanying drawings. In these drawings:

FIG. I is a diagrammatic overall view of the paster;

FIG. 2 is an enlarged view of the main part of the paster;

FIG. 3 is a section on the line III-III in FIG. 2;

FIG. 4 is an enlarged longitudinal section of the transfer drum; and

FIG. 5 is an enlarged fragmentary section in a horizontal plane, showing the transfer drum picking up paste from the pickup drum.

As shown in FIG. 1, the paster includes a reservoir 10 in which paste 12 is maintained in a melted condition during use. For this purpose the reservoir may for example be surrounded by any suitable form of heater. A gear pump 14 delivers the paste up through a pipe 16 at a pressure of approximately 100 p.s.i. At the upper end of the pipe 116 the paste enters the upper end of a vertical groove 18 in a stationary housing 20 extending along a pickup drum 22. The excess paste which is not picked up by the drum 22 passes down the groove 18 and is discharged back into the reservoir 10 through a return pipe 23.

The pipe 16 may be surrounded by an electrical heating coil for use in an emergency. Normally, any adhesive remaining in the groove 18 or pipe 16 will flow downwards back into the reservoir 10 at the end of a period of operation. For this purpose it should be noted that the upper end of the pipe 116 inclines towards the upper end of the groove l3, so as to include no horizontal or near-horizontal section.

The pickup drum 22 rotates about a vertical axis and receives a coating of adhesive from the groove T8. In particular adhesive is received in pitted areas in the drum 22 against which sponge rubber transfer members on a transfer drum 24 roll so as to pick up adhesive which is then applied for example to a sheet of paper or to a length of paper webbing held by a backing member 26. The transfer strips are shown in FIG. 2 and will be described further on. With further reference to FIG. 2, it should be noted that any adhesive which runs down either of the drums 22 or 24 is conveyed by a sloping floor 28 to the return pipe 23 leading back to the reservoir 10.

The paster may be used to apply adhesive to the paper sections used to form soft packets for cigarettes as described in French Pat. No. 1,498,097. The paster is shown in FIGS. 2 and 15 of that application. The paste in that case is applied to the paper after it has been cut from a continuous web, the individual pieces of paper being held by suction on the blocks 15 which rotate bodily about the vertical axis of rotation of the packing machine as a whole. In other words, the blocks 15 (equivalent to the backing member 26 shown in the present application) have convex outer surfaces centered on the axis of rotation of the machine.

With reference to FIGS. 2 and 3 of the present application, it will be seen that the pickup drum 22 has one vertical pitted strip area 30 and one circumferential strip area 32. These are matched by vertical and circumferential striplike transfer members 34 and 36 on the transfer drum 24. These members 34 and 36 are of moulded sponge rubber. The drums 22 and 24 rotate at the same speed and are of the same diameter so that the transfer members 34 and 36 register once during each revolution respectively with the pitted strip areas 30 and 32. The distance between the axes of the drums 22 and 24 is such that there is an interference fit as regards the sponge rubber transfer members 34 and 36; this insures that the rubber enters the pitted areas of the pickup drum to pick up an adequate quantity of adhesive. It is significant to note that the use of sponge rubber in this context, owing to its compressibility means that the positioning of the axes of the drums 22 and 24 is not highly critical. Similarly, the position of the backing member 26 for the paper in relation to the transfer drum 24 is not highly critical since again there can be an interference fit between the transfer members 34 and 36 on the one hand and the backing member on the other hand. The surface of the backing member along which the transfer drum 24 moves with a rolling action is shown in dotted outline in FIG. 3.

The bottom end of the groove 18 is defined by a plate 78 which provides a restricted aperture 80 through which the adhesive flows downwards out of the groove 18 to return to the reservoir 10. This aperture may be smaller than that shown, in order to maintain the adhesive in the groove 18 at a definite pressure. Instead of the aperture 80 being formed as a notch in the edge of the plate 78, the edge of the plate may fit closely round the drum 22 to form a reasonable seal, and the aperture may be in the form of a small-diameter hole drilled through the plate 78.

The upper extremity of the groove 18 in the casing 20 is defined by a member 38 (see FIG. 2) which fits closely against the drum 22 so as to form a seal. As shown in FIG. 3, there is no seal immediately adjacent to the longitudinal sides of the groove 18, but there are members 40 and 42 which extend longitudinally with respect to the drum 22 and confine the adhesive, the member 40 being a spring-molded strip, whereas the member 42 is a rod basically of cylindrical shape through with a cutout 44. One edge 46 of the rod 42 is a close fit against the surface of the drum 22; the angular position of the rod 42 about its axis is adjustable so as to ensure a close sealing fit. As an alternative, the rod 42 may have a radial lever arm at one end lying outside the casing, and a spring may act on that lever arm so as to urge the edge 46 against the drum 22 by tending to rotate the rod in a counterclockwise direction as viewed in FIG. 3.

The directions of rotation of the drums are shown by arrows in FIG. 3. It will be seen that the strip 40 also acts as a scraper which will remove any adhesive remaining on the surface of the drum 22 before fresh adhesive is picked up by the drum while passing the groove 18. This ensures that the adhesive is continuously circulating and does not remain on the drum with the consequent possibility of it setting. Any adhesive which is removed by the member 40 drops on to the sloping floor 28 and is returned to the reservoir through the pipe 23.

It will be seen that the bottom end of the drum 22 is lower than that of drum 24. This ensures that any adhesive which does run down the surface of the drum 22 and is finally flung off at the bottom of the drum 22 will not pass on to the drum 24.

As shown in FIG. 5, the vertical sponge rubber transfer member 34 is clamped in position by means of screws acting on a curved plate 48 which has a slot through which the main part of the member 34 projects. The member 34 has a longitudinal bore 52 so that any excess adhesive drawn into the cells of the sponge rubber can pass down the bore 52 and return to the reservoir via the sloping floor 28. The circumferential transfer member 36 may be secured similarly to the drum 24.

The use of sponge rubber with interconnecting cells for transferring adhesive from the drum 22 to the workpiece provides an effective means of transferring sufficient quantities of adhesive without allowing a significant amount of adhesive to be thrown off in an uncontrolled fashion. Moreover the interconnecting cells ensure that the rubber does not expand and distort when hot.

FIG. 4 shows the manner of mounting the transfer drum 24. The drum has an internal flange 53 by which it is secured and keyed to a shaft 54 which carries a gear 56 at its lower end. This gear meshes with a similar gear on a shaft within the drum 22, this last shaft being connected to a input shaft 58 shown in FIG. 2. The shaft 54 for the drum 24 is mounted in bearings 60, 62 and 64 contained within a stationary member 66 which at its upper end extends into the drum 24. The mounting ofthe drum 22 may be generally similar, except that the stationary part can in that case extend further upwards into the drum, and the top bearing (equivalent to the bearing 60) can be nearer the middle of the drum. This is prevented in the case of the drum 24 by the presence of a stationary core 68 which extends into the drum 24 from the top, being secured to a casing part 70 by screws 72, and contains three heating elements 74 and a central thermostat 75 (see also FIG. 3). These may for example maintain the drum 24 at a temperature of 90 to 1 10 C. to ensure that the adhesive does not set while on the drum 24. The temperature of the adhesive in the reservoir 10 (FIG. 1) may for example be 120 to 140 C.

The drum 24 has a spaced shroud 76 which helps to prevent The paster as shown in the drawings is particularly useful for applying hot-melt adhesive which is pressure sensitive, that is to say remains tacky" even after it has cooled. Such an adhesive is described in British Pat. application No. 5012 l/68.

We claim:

1. Apparatus for applying especially a low-viscosity hotmelt adhesive to a vertical workpiece, comprising a reservoir for the adhesive having a delivery passage and a return passage connected with it; a housing having a vertical groove in it, the top end of the groove being connected to the delivery passage and the bottom end of the groove being connected to the return passage; means for feeding adhesive from the reservoir to the vertical groove through the delivery passage; and a pickup drum mounted in the housing for rotation about a vertical axis and adjacent to the groove; whereby the drum picks up adhesive from the groove as it rotates, and excess adhesive flows back to the reservoir through the return passage.

2. Apparatus according to claim 1 including a transfer drum mounted for rotation about a vertical axis and comprising at least one transfer member which rolls in contact with at least one predetermined area of the pickup drum to receive adhesive, and is arranged to roll in contact with a vertical work piece so as to transfer adhesive to the workpiece over an area corresponding to the said predetermined area.

3. Apparatus according to claim 2 in which the said predetermined area of the pickup drum is pitted.

4. Apparatus according to claim 3 including a scraper which scrapes adhesive off the unpitted area of the pickup drum.

5. Apparatus according to claim 3 in which the transfer member is of sponge rubber.

6. Apparatus according to claim 5 in which the sponge rubber has a high proportion of interconnecting cells.

7. Apparatus according to claim 5 in which the axes of the pickup drum and transfer drum are so positioned that the transfer member is compressed between the two drums so as to be forced into the hollows of the pitted area of the pickup drum.

8. Apparatus for applying a low-viscosity hot-melt adhesive by rolling contact with a vertical workpiece, comprising a heated reservoir for the adhesive, a pump for delivering adhesive upwards from the reservoir through a delivery pipe extending to a double drum device, and a return pipe for returning excess adhesive from the double drum device downwards back into the reservoir, the said double drum device comprising a housing, a pickup drum mounted for rotation in the housing about a vertical axis, a transfer drum also mounted for a rotation in the housing about a vertical axis, and means defining a vertical groove in the housing which extends down one side of the pickup drum and has its upper and lower ends connected respectively to the delivery pipe and return pipe, the said transfer drum comprising at least one compressible transfer member which picks up adhesive from the pickup drum and applies it to the workpieces with a rolling motion.

9. Apparatus according to claim 8 in which the transfer member picks up adhesive from a pitted area on the pickup drum, and including means for scraping adhesive off the unpitted area of the pickup drum.

10. Apparatus according to claim 9 in which the transfer member is of sponge rubber.

11. Apparatus according to claim 8 including means for heating the transfer drum.

12. Apparatus for applying a low-viscosity hot-melt adhesive by rolling engagement with at least one predetermined area of a workpiece, comprising a transfer drum which is arranged to roll in contact with the workpiece and includes a transfer member of rubber or rubberlike material of spongelike formation with a high proportion of interconnecting cells which stands proud from the main cylindrical peripheral surface of the drum and is shaped so as to apply the adhesive to the said predetermined area of the workpiece; a pickup drum positioned to roll in contact with the transfer member and having a peripheral surface which is smooth except for a pitted area which corresponds in shape to, and cooperates with, the transfer member of the transfer drum, the pickup drum being arranged to rotate adjacent to a pool of adhesive so as to pick up adhesive on its peripheral surface, and a scraper in continuous contact with the surface of said pickup drum which removes substantially all adhesive from the smooth part of the peripheral surface of the pickup drum 

1. Apparatus for applying especially a low-viscosity hot-melt adhesive to a vertical workpiece, comprising a reservoir for the adhesive having a delivery passage and a return passage connected with it; a housing having a vertical groove in it, the top end of the groove being connected to the delivery passage and the bottom end of the groove being connected to the return passage; means for feeding adhesive from the reservoir to the vertical groove through the delivery passage; and a pick-up drum mounted in the housing for rotation about a vertical axis and adjacent to the groove; whereby the drum picks up adhesive from the groove as it rotates, and excess adhesive flows back to the reservoir through the return passage.
 2. Apparatus according to claim 1 including a transfer drum mounted for rotation about a vertical axis and comprising at least one transfer member which rolls in contact with at least one predetermined area of the pick-up drum to receive adhesive, and is arranged to roll in contact with a vertical workpiece so as to transfer adhesive to the workpiece over an area corresponding to the said predetermined area.
 3. Apparatus according to claim 2 in which the said predetermined area of the pick-up drum is pitted.
 4. Apparatus according to claim 3 including a scraper which scrapes adhesive off the unpitted area of the pick-up drum.
 5. Apparatus according to claim 3 in which the transfer member is of sponge rubber.
 6. Apparatus according to claim 5 in which the sponge rubber has a high proportion of interconnecting cells.
 7. Apparatus according to claim 5 in which the axes of the pick-up drum and transfer drum are so positioned that the transfer member is compressed between the two drums so as to be forced into the hollows of the pitted area of the pick-up drum.
 8. Apparatus for applying a low-viscosity hot-melt adhesive by roLling contact with a vertical workpiece, comprising a heated reservoir for the adhesive, a pump for delivering adhesive upwards from the reservoir through a delivery pipe extending to a double drum device, and a return pipe for returning excess adhesive from the double drum device downwards back into the reservoir, the said double drum device comprising a housing, a pick-up drum mounted for rotation in the housing about a vertical axis, a transfer drum also mounted for rotation in the housing about a vertical axis, and means defining a vertical groove in the housing which extends down one side of the pick-up drum and has its upper and lower ends connected respectively to the delivery pipe and return pipe, the said transfer drum comprising at least one compressible transfer member which picks up adhesive from the pick-up drum and applies it to the workpieces with a rolling motion.
 9. Apparatus according to claim 8 in which the transfer member picks up adhesive from a pitted area on the pick-up drum, and including means for scraping adhesive off the unpitted area of the pick-up drum.
 10. Apparatus according to claim 9 in which the transfer member is of sponge rubber.
 11. Apparatus according to claim 8 including means for heating the transfer drum.
 12. Apparatus for applying a low-viscosity hot-melt adhesive by rolling engagement with at least one predetermined area of a workpiece, comprising a transfer drum which is arranged to roll in contact with the workpiece and includes a transfer member of rubber or rubber-like material of sponge-like formation with a high proportion of interconnecting cells which stands proud from the main cylindrical peripheral surface of the drum and is shaped so as to apply the adhesive to the said predetermined area of the workpiece; a pick-up drum positioned to roll in contact with the transfer member and having a peripheral surface which is smooth except for a pitted area which corresponds in shape to, and cooperates with, the transfer member of the transfer drum, the pick-up drum being arranged to rotate adjacent to a pool of adhesive so as to pick up adhesive on its peripheral surface, and a scraper in continuous contact with the surface of said pick-up drum which removes substantially all adhesive from the smooth part of the peripheral surface of the pick-up drum. 